The Audiology Clinic traditionally collaborates with many branches within most institutes of the NIH, including the lnter-Institute Genetics Program. In addition to the data supplied to the principal investigator and the service component the Clinical Audiology Unit develops data on hearing and auditory/vestibular system function in diverse disease processes. This year the major clinical research effort has been in defining auditory/vestibular parameters in Neurofibromatosis Type 2; inherited neurodegenerative metabolic disorders in children; Aging Downs Syndrome; Alzheimer's Disease; Ototoxic effects of chemotherapeutic regimens in various cancers; Thalasemmia and Iron Overload; Osteogenesis Imperfecta and Precocious Puberty (four types). Formal presentations and publications from this work are produced. The assessment of auditory function is achieved through detailed study of puretones and speech sensitivity; suprathreshold studies of speech recognition; biomechanical measurement of middle ear function, including multi-frequency tympanometry and electrophysiologic study of auditory evoked potentials. Test strategies are developed for each disorder, condition or therapeutic regimen to elicit the appropriate information for each target population. Additional tests such a cochlear emissions, trans- tympanic electrocochleography and posturography will be added to the test battery for certain populations as normative data on these new clinical tools is developed. There is almost no body of audiologic or medical literature describing or defining the hearing or other auditory system deficits in descriptions of diverse disease processes in providing new audiologic data in these conditions, this protocol not only enhances patient care but responds to the charge of the NIDCD to find define and manage causes of deafness and hearing impairment. It expands our understanding of the broad role of the auditory system in many diseases and further identifies entire populations of individuals who have not been considered in the epidemiology of deafness and hearing impairment.